In high-frequency (RF) surgery it is known to devitalize tissue in a targeted manner by means of the application of RF current. Such an operation can be performed with the use of a monopolar or bipolar instrument. With the use of a monopolar instrument, the current path usually leads from the electrosurgical instrument via the tissue to be treated to the neutral electrode. With the use of a bipolar instrument, the instrument is designed to have two sections that are electrically insulated from each other so the current path extends from a first section of the electrosurgical instrument via the tissue to be treated to a second section of the electrosurgical instrument.
Cryoprobes including distal and proximal electrodes for applying the appropriate current are known. These cryoprobes include a cooling device that allows cooling of the tissue that is in direct contact with the instrument. In doing so, it is possible to prevent any unwanted carbonization of the surrounding tissue, so that the instrument can be used for a controlled and potentially larger area devitalization. Furthermore, by using the cooling device in a targeted manner, the heat distribution can be controlled along the instrument, and thus the devitalization region can be adjusted.
Appropriate cooling can be accomplished, for example, by the targeted use of the Joule-Thomson effect. In this case, a fluid, in particular a gas, experiences a temperature change due to throttling (pressure change).
Electrosurgical instruments including a distal electrode and a proximal electrode provided on the outside of a probe tube are known.
A fluid or gas channel, within the lumen, can provide a cooling fluid to an expansion chamber at the distal end of the probe tube. The lumen of the probe tube is used to discharge the expanded fluid. To electrically connect the distal and the proximal electrodes with an RF generator, some electrodes may use a fluid or gas channel that is electrically conductive, and others may use a conductive lead that is separately arranged within the lumen and insulated relative to the gas channel. The electrical connection of the proximal electrode to the other conductive lead is difficult. Thus, openings are provided in the probe tube in order to provide appropriate electrical contact. The fluid transported in the lumen can then exit the lumen through these openings into the tissue and cause damage. Furthermore, the probes must have dimensions such that the lumen offers sufficient space for the accommodation of the additional lead. It is difficult to manufacture such probes while maintaining the small probe size necessary for minimally invasive procedures.
Publication EP 1 902 683 A1 has disclosed a catheter for the application of a current. To do so, the catheter comprises several electrodes that are supplied with a suitable voltage via the conductive path within a sheathing of the catheter. The conductive paths are located inside the exterior wall of the sheathing and are electrically insulated relative to each other.